1. Field of the Invention
The present invention relates to an image forming device which is preferably used in a printer, a facsimile machine and a copying machine or the like and forms an image such as a character and a figure on printing paper.
2. Description of Related Art
A printer, a facsimile machine and a copying machine are a known image forming device for printing an image such as a character and a figure onto printing paper. FIG. 8 shows an example of an image forming unit of a conventional image forming device. A charging device 901 impressed with a prescribed bias voltage charges a surface of a photoconductive drum 902. According to image information, a Light Emitting Diode (LED) head 903 selectively exposes the photoconductive drum 902 and an electrostatic latent image is formed on the surface of the photoconductive drum 902. A charged toner 911 is supplied from a developing device 904 to the electrostatic latent image and a toner image is formed. The toner image is transferred onto printing paper 910 by a transfer roller 905 impressed with a prescribed bias voltage. Then, a fuser device 906 applies heat and pressure to the toner image on the printing paper and the toner image is fixed on the printing paper. Meanwhile, after the transfer process, a surface charge of the photoconductive drum 902 is eliminated by a charge eliminating device 907, and a toner remaining on the surface of the photoconductive drum 902 is removed by a cleaning device 908. Then, the photoconductive drum 902 is charged again by the charging device 901.
In the above-described image forming device, the charging device 901, the photoconductive drum 902, the developing device 904, the charge eliminating device 907 and the cleaning device 908 are accommodated in a cartridge as a process unit 900. The process unit 900 is configured to be capable of being inserted and removed with respect to a device main body. Accordingly, when maintenance work is necessary, for example, when the photoconductive drum 902 wears out or when the toner runs out, each of the devices 901, 902, 904, 907 and 908 can be replaced integrally. As a result, the maintenance work can be carried out easily.
Under a state in which the process unit 900 is inserted in the device main body, the photoconductive drum 902 and the transfer roller 905 in the device main body are making contact with one another. Therefore, when removing the process unit 900 from the device main body, the process unit 900 is preferably moved in a radial direction of the photoconductive drum 902, that is, a direction in which the process unit 900 separates from the transfer roller 905. That is, if the process unit 900 is removed upward in FIG. 8, when inserting or removing the process unit 900, the photoconductive drum 902 and the transfer roller 905 are less likely to be rubbed against one another. As a result, the surface of the photoconductive drum 902 is difficult to damage. Since the process unit 900 is removed in such a direction, in a conventional image forming device, an openable and closable cover is provided on an upper surface or a side surface of the image forming device, and by opening the cover, the process unit 900 is inserted or removed.
Conventional Office Automation (OA) equipment, such as the printer, the facsimile machine and the copying machine is preferably compact in consideration of saving space in an office. However, if an image forming device is configured so that the process unit 900 is inserted or removed from a side of the device main body like the above-described conventional image forming device, space for opening and closing the cover is required to be secured at a side of the device main body. Therefore, from aspects of saving space and convenience of work, the image forming device is preferable to be configured so that a user can make access to the process unit 900 from a front side of the image forming device.
In case of removing the process unit 900 from the front side of the device main body, the process unit 900 is moved in an axial direction of the photoconductive drum 902, in other words, to the front side of the page of FIG. 8. Therefore, the transfer roller 905 is required to be separated from the photoconductive drum 902 in advance so that the surface of the photoconductive drum 902 is not damaged.
If the space for separating the transfer roller 905 is secured sufficiently, the image forming device cannot be downsized. Furthermore, from an aspect of the costs, a number of new additional members for separating the transfer roller 905 is required to be minimized as much as possible.